Metachronous Pancreatic Ductal Adenocarcinoma with Adjacent Serous Cystadenoma that Was Preoperatively Diagnosed by EUS-FNA: A Case Report and Review of the Literature

Abstract

Pancreatic serous cystic neoplasms (SCNs), such as serous cystadenoma (SCA), are generally recognized as benign because malignant counterparts of SCNs have been extremely rare. In clinical practice, pancreatic cystic neoplasms diagnosed as SCNs have been managed by conservative observation, as long as the patients remained asymptomatic. We herein report a case of metachronous ductal adenocarcinoma that was discovered during long-term follow-up of SCN and review the related literature. To our knowledge, this was the first reported case of the local presence of ductal adenocarcinoma adjacent to SCA that was preoperatively diagnosed by endoscopic ultrasound-guided fine-needle aspiration.

Keywords: diffusion-weighted magnetic resonance image (DWI); endoscopic ultrasound-guided fine needle aspiration (EUS-FNA); pancreatic ductal adenocarcinoma (PDAC); serous cystadenoma (SCA); serous cystic neoplasm (SCN).

Figure 1.

Images obtained at the initial presentation. a) Contrast-enhanced computed tomography (CT) and (b) magnetic resonance cholangiopancreatography (MRCP) show a 36×34-mm multilobulated and heterogeneous cystic mass in the head of the pancreas. (c) Endoscopic ultrasonography (EUS) shows a honeycomb appearance and a central stellate scar in the cystic mass.

Figure 2.

Serial images during routine checkup. (a) Serial MRCP images after the SCN diagnosis show no remarkable change in the multilobulated cystic mass. After six years, the cystic mass has started obstructing the passage of the main pancreatic duct (MPD), resulting in dilation of the tail side of the MPD. (b) EUS at six years after the initial presentation shows no remarkable change in the characteristics of the cystic lesion (left panel). The common bile duct (CBD) (arrow) is not dilated (middle panel), but the cystic mass is obstructing the MPD, causing subsequent dilation of the tail side of the MPD (arrowhead; right panel).

Figure 3.

Images obtained eight years after the initial presentation. (a) Contrast-enhanced CT shows a 48×45-mm heterogeneous cystic tumor in the head of the pancreas and biliary obstruction. (b) MRCP shows dilation of both the MPD and CBD.

Figure 4.

Images obtained eight years after the initial presentation. (a) EUS shows part of the SCN causing CBD obstruction and subsequent upstream dilation (left panel). Careful EUS shows a neighboring solid tumor as the direct cause of CBD obstruction (middle panel). EUS-guided fine-needle aspiration (EUS-FNA) is performed to obtain tissue samples from the solid lesion (right panel). (b) Pathological images of the pancreatic tissue specimens obtained by EUS-FNA show the presence of adenocarcinoma (Hematoxylin and Eosin staining; original magnification, ×400). (c) Endoscopic retrograde cholangiography shows distal obstruction of the CBD with dilation of the hilar BD.

Figure 5.

Pathological images of the resected specimen. (a) Grossly, the specimen resected by subtotal stomach-preserving pancreaticoduodenectomy shows a lobulated cystic tumor replacing the head of the pancreas and confirms the presence of a 22×15-mm solid tumor (arrow) adjacent to the cystic tumor. (b) A whole-mount sample stained with Hematoxylin and Eosin staining (upper panel) shows ductal adenocarcinoma in the solid tumor (PDAC) (middle panel; original magnification, ×200) that is adjacent to a serous cystadenoma (SCA) (lower panel; original magnification, ×200), with a relatively clear border.

Figure 6.

Immunohistochemical staining of the pathological images. Inhibin is positive in the SCA sample (a) (original magnification, ×100) but not in the PDAC sample (b) (original magnification, ×100). MUC6 is positive in the SCA sample (c) (original magnification, ×100) but not in the PDAC sample (d) (original magnification, ×100). MUC6: mucin 6, PDAC: pancreatic ductal adenocarcinoma, SCA: serous cystadenoma

Figure 7.

Serial images of diffusion-weighted MRI during routine checkup. At seven years after the initial presentation, before the occurrence of obstructive jaundice, the image shows no intense signal (left panel). Six months later, a focal hyperintense signal is seen in the pancreatic head (middle panel). After another six months, at the time of the occurrence of obstructive jaundice, the focal signal is more obvious (right panel).